Coating for cutting implements

ABSTRACT

A cutting implement having a pair of cutting blades and a coating is provided. The coating has titanium chromium nitride and provides the cutting blades with a satin silver appearance. In some embodiments, the titanium chromium nitride coating has a thickness in a range between about 0.3 microns and 0.5 microns, a surface roughness in a range of about 15 to 25 10 −6  inch/inch, and a hardness in a range of about 5.7 to about 9.1 gigapascals.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/720,578 filed Nov. 24, 2003, incorporated herein by reference. U.S.application Ser. No. 10/720,578 is a continuation of InternationalApplication No. PCT/US02/36314 filed Nov. 13, 2002, which claimspriority from Provisional Application No. 60/338,575, filed Nov. 13,2001.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to stationery cutting implements suchas scissors, shears, guillotine style paper trimmers, and rotary stylepaper trimmers. More particularly, the present invention is related to acoating for such cutting implements.

2. Description of Related Art

Substantial effort has been expended in improving the construction andoperation of stationery cutting implements for household and office use.Ever increasing demands have been placed on manufacturers of theseproducts to increase the ease of use, the wear resistance, and the easewith which the products can be cleaned, while maintaining a competitiveprice. For example, typical household and office scissors have beenunable to achieve a long-lasting cutting edge, which withstands thewide-variety of products being cut, at a competitive price.

Consequently, continued improvements in stationery cutting implements isdesired.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to provide a cutting implementhaving a coating that provides one or more of improved wear resistance,increased hardness, pleasing appearance, reduced user effort, andincreased stain resistance.

These and other objects of the present invention are provided by acutting implement comprising a pair of cutting blades and a coating. Thecoating comprises titanium chromium nitride, which provides the cuttingblades with a satin silver appearance. A cutting implement having a pairof complementary cutting blades and a titanium chromium nitride coatingis also provided. The titanium chromium nitride coating is disposed oneach of the cutting blades. The titanium chromium nitride coating has athickness in a range between about 0.3 and 0.5 microns, a surfaceroughness in a range of about 15 to 25×10⁻⁶ inch/inch, and a hardness ina range of about 5.7 to about 9.1 gigapascals.

The above-described and other features and advantages of the presentinvention will be appreciated and understood by those skilled in the artfrom the following detailed description, drawings, and appended claims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a first side view of an exemplary embodiment of a pair ofscissors;

FIG. 2 is a second, opposite side view of FIG. 1;

FIGS. 3 and 4 are side views of the blades of FIG. 1;

FIG. 5 is a data table of testing results of various exemplaryembodiments of a coating of the present invention for the scissors ofFIG. 1;

FIG. 6 is a perspective view of an exemplary embodiment of a rotarystyle paper trimmer;

FIG. 7 is a sectional view along line 7-7 of FIG. 6;

FIG. 8 is a perspective view of an exemplary embodiment of a guillotinestyle paper trimmer; and

FIG. 9 is a side view of the guillotine style paper trimmer of FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the figures and in particular to FIGS. 1 and 2, acutting implement in the form of pair of scissors generally indicated byreference numeral 10 is illustrated.

Scissors 10 have a first half 12 pivotally connected to a second half14. First and second halves 12, 14 are pivotally connected byconventional connection means, such as a screw 16 and a post 18. Firsthalf 12 can have a handle 20 and a blade 22. Similarly, second half 14can have a handle 24 and a blade 26.

Each blade 22, 26 has a cutting edge 28. Preferably, cutting edge 28 isformed by way of a bevel 30 disposed on each blade 22, 26, respectively.Thus, scissors 10 provide a pair of complementary cutting blades 22, 26for cutting stationery products, such as paper, cardboard, Bristolboard, and others.

Handles 20, 24 are preferably overmolded onto blades 22, 26,respectively. However, it should be recognized that each half 12, 14 ofscissors 10 is described as having separate handles 20, 24 overmoldedonto blades 22, 26, respectively. Of course, it is contemplated by thepresent invention that each half 12, 14 have a unitary handle and bladeportion.

Blade 22 is illustrated in FIG. 3, while blade 26 is illustrated in FIG.4. Blades 22, 26 are preferably made of steel, more preferably stainlesssteel, such as 420 stainless steel. In addition, blades 22, 26 can beheat-treated to further increase the hardness of the blades.

Scissors 10 further include a coating 32 disposed on each blade 22, 26.Coating 32 provides cutting edges 28 with extremely tough, hard, wearresistant characteristics. The increased hardness of cutting edges 28provides scissors 10 with substantially increased longevity, while alsoproviding the scissors with corrosion resistance, as well as providing asmooth and uniform appearance and color. For example, scissors 10 havingcoating 32 were subjected to cycle testing of 10,000 openings andclosings without showing any signs of wear to the coating.

In addition, coating 32 provides scissors 10 with an aestheticallyacceptable color or appearance. Specifically, coating 32 differentiatesblades 22, 26 having coating 32 from uncoated blades. Coating 32 doesnot change the color of blades 22, 26 to the point that the consumer nolonger recognizes scissors 10 as being useable for general household andoffice use. However, coating 32 has an appearance sufficient to allowthe consumer to recognize that the coating is present on scissors 10.

Further, coating 32 increases the ease of use of scissors 10 byproviding blades 22, 26 with a smooth surface finish, which reducesfriction between the blades during use. Thus, blades 22, 26 have lessfriction between the two inside blade faces, which provides a smoothercutting action and less cutting effort than in blades without coating32.

Coating 32 is selected from the group consisting of titanium nitride(TiN), chromium nitride (CrN), and titanium chromium nitride (TiCrN).More preferably, coating 32 is a multiple component barrier of titaniumchromium nitride.

Coating 32 is disposed on blades 22, 26 such that the coating forms ametallurgical bond with the blades, which resists flaking, blistering,chipping, and peeling. In fact, coating 32 is absorbed into the surfacelayer of the metal of blades 22, 26. Coating 32 is disposed on blades22, 26 with a thickness in a range between about 0.3 and 0.5 microns,more preferably about 0.4 microns.

FIG. 5 illustrates the test results for a range of compositions andprocesses for coating 32. Sample 1 is a control or uncoated blade formedof heat-treated 420 stainless steel. Heat-treated 420 stainless steelblades were also used in Samples 2 through 10.

In Samples 2 through 6, the blades were coated using a first process.Twelve (12) blades of each sample coating were prepared with a thicknessof about 5.0 micrometers. In Samples 7 through 10, the blades werecoated using a second process. All of the samples were then tested forsurface smoothness, hardness, and color. The results of this testing areprovided in FIG. 5.

The concentration of coating 32 in all samples were tested and were inthe range of about +/−3 to 4 percent of the target composition. Thetesting also showed that both the elements are uniformly deposited andthere is no segregation or isolation of each to any particular region inthe film.

The first process was a reactive magnetron sputtering with a pulsed dcsource. The second process comprised a cathode arc plasma (CAP) process.The sputtering gas mixture in each process was argon and nitrogen.

In the first process, a four-inch circular target is used with a pulseddc power supply. The target was a combination target having one or more90-degree sections of pure titanium and chromium. For example, in Sample#3 the target is three 90-degree sections of pure titanium and one90-degree section of pure chromium.

In the second process, two different targets were used simultaneously,with each target being pure titanium and chromium.

The partial pressure of argon during the first process was maintainedbetween 0 to 1 millitorr and that of nitrogen was maintained at 1 to 2millitorr with the total sputtering gas pressure maintained between 2 to3 millitorr. The stainless steel chamber was evacuated to 2×10⁻⁵ Torrprior to the deposition. Cleaning of the target was carried with argonalone. The sputtering current was kept at 0.3 amps during cleaning thatwas carried out for 3 minutes in all depositions. Deposition of thefilms on the blades during cleaning was prevented by a shutter that waswithdrawn soon after cleaning the target. The sputtering current waschosen at two different values, 0.5 amperes and 0.7 amperes. Depositionswere performed for two different total sputtering times, 15 minutes and30 minutes. The resulting thickness of the films was found to be 0.3micrometers and 0.6 micrometers, respectively. The depositiontemperature has been optimized for the following conditions. Stainlesssteel scissors blades should not soften and therefore depositiontemperature was kept at a temperature of about 150° and 200° C.

The hardness of the samples was measured using a Vickers microhardnesstest according to American Society of Testing and Materials (ASTM) E384,last revised March 2001. Here, a diamond indenter is loaded to a desiredamount, which causes the indenter to indent the sample. The indentationis measured and converted to a hardness value. The indenter is athree-sided, pyramid shaped diamond probe tip with angle of 136°. Thehardness values of FIG. 5 represent the hardness of each sample withload of about 50 grams, with a load of about 400 grams for the uncoatedsample 1

The results of FIG. 5 show that the coated samples (samples 2 to 10) aregenerally harder than the uncoated sample (sample 1). For example,sample 4 is about 125% harder than sample 1. Further, the results ofFIG. 5 show that the hardness of the coated samples (samples 2 to 10)generally tends to increase as the content of chromium increases.

In addition, the results of FIG. 5 show that the silver appearancegenerally tends to increase as the content of chromium increases.

The samples having a majority of chromium (e.g., samples 6 and 10) had agloss silver appearance, which was substantially similar to that ofuncoated samples 1. In fact, it has been determined that consumers didnot recognize that the scissors having a gloss silver appearance (e.g.,the samples having a majority of chromium) had any coating at all.

In contrast, the samples having a majority of titanium (e.g., samples 2,3, 7 and 8) had a satin gold appearance. Here, it has been determinedthat consumers recognized scissors having a satin gold appearance (e.g.,the samples having a majority of titanium) as being for uses other thangeneral household and office use. Namely, these scissors appear to theconsumer to be specialty scissors.

However, the samples having a more balanced amount of titanium tochromium (e.g., samples 4, 5, and 9) had a satin silver appearance.Here, it has been determined that consumers recognized scissors 10having a satin silver appearance as being for general household use andas having a coating.

Chromium is typically about 2.5 times more expensive than titanium.Thus, forming coating 32 of a majority of chromium leads to asubstantial increase in cost, with only minimal gains in hardness. Forexample, coating 32 having 75% chromium and 25% titanium is about 95% ashard as a coating of 100% chromium.

It has also been found that the chromium nitride forms a strong bond tothe blade, but does not form a strong bond with itself. For example,chromium nitride can form a strong bond with the chromium oxide of blade22, 26, but does not form a strong bond with other chromium nitridemolecules. Thus, the samples having a majority of chromium exhibited ahigher tendency to peep than other samples having a minority ofchromium.

The diffusion barriers properties exhibited by the samples having amajority of titanium were superior to those having less titanium. Thus,the samples having a majority of titanium exhibited better stain andcorrosion resistance than other samples having a minority of titanium.

Coating 32 having the desired hardness, smoothness, and diffusionbarrier properties preferably is formed of titanium chromium nitridehaving about 35 percent by weight of titanium nitride and about 65percent by weight of chromium nitride and with a hardness in a range ofabout 5.7 to about 9.1 gigapascals. More preferably, coating 32 hasabout 50 percent by weight of titanium nitride and about 50 percent byweight of chromium nitride and a hardness in a range of about 7.2 toabout 7.6 gigapascals.

It has been determined that coating 32 having the aforementioned ratiosof chromium nitride and titanium nitride provided scissors 10 with avisual indication that the coating had been applied, without affectingthe consumer's impression of the target use of the scissors (i.e.,general household use). Moreover, coating 32 having the aforementionedratios of chromium nitride and titanium nitride provided scissors 10with drastically improved hardness over the uncoated sample 1.

The surface roughness of blades 22, 26 before and after the applicationof coating 32 was also measured. For example, the surface roughness ofthe outside surface of blades 22, 26 before coating 32 was in a range ofabout 20 to 25×10⁻⁶ inch/inch after the coating was applied. It isbelieved that the roughness of blades 22, 26 was reduced because themolecules of coating 32 predominantly bond with the valleys andindentations in the blades.

Of course, it should be recognized that scissors 10 are described aboveby way of example only as having a coating applied by reactive magnetronsputtering and CAP processed. Any thin film forming method such aschemical vapor deposition, physical vapor deposition, thermal sprayingand sintering after a dip coating may be employed for providing coating32 to scissors 10. Preferably, the method of forming coating 32 has amaximum temperature sufficient to not soften or affect theheat-treatment of the uncoated blades.

It should also be recognized that coating 32 has been described above byway of example only as finding use with a cutting implement in the formof scissors 10. Of course, coating 32 can provide the aforementionedbenefits to other stationary cutting implement. For example, FIGS. 6 to9 illustrate alternate exemplary embodiments of cutting implements,which have a coating.

An exemplary embodiment of a cutting implement in the form of a rotarystyle paper trimmer 110 is illustrated in FIGS. 6 and 7. Rotary stylepaper trimmer 110 is as shown and described in U.S. ProvisionalApplication Ser. No. 60/421,581 filed on Oct. 28, 2002, the contents ofwhich are incorporated herein by reference.

Trimmer 110 has a base 112 and a rotary cutting mechanism 114. Base 112has a rail 116 and a cutting blade or anvil 118. Rotary cuttingmechanism 114 has a circular cutting blade 120 disposed in a housing122. Housing 122 is slideably received on rail 116.

Blade 120 is disposed in housing 122 opposite blade 118 as illustratedin FIG. 7. Blade 120 has a cutting edge 124 formed at its outerperiphery, while blade 118 has a corresponding cutting edge 126. Rotarycutting mechanism 114 is also movably received on rail 116 such thatcutting edges 124, 126 can be moved into contact with one another.Accordingly, trimmer 110 has a pair of complementary cutting blades 118,120.

During use of trimmer 110, a piece of paper 128 is positioned betweencutting edges 124, 126. Rotary cutting mechanism 114 is moved such thatcutting edge 124 is contact with cutting edge 126. Then, rotary cuttingmechanism 114 is slid along rail 116 such that the interaction ofcutting edge 124 on cutting edge 126 severs paper 128 disposedtherebetween.

Blades 118, 120 are preferably made of steel, more preferably stainlesssteel, such as 420 stainless steel. In addition, blades 118, 120 can beheat-treated to further increase the hardness of the complementarycutting blades.

Trimmer 110 has a coating 132 disposed on blades 118, 120. As describedin detail above with respect to the exemplary embodiments of FIGS. 1 to5, coating 132 has a thickness in a range between about 0.3 microns,more preferable about 0.1 microns.

Coating 132 provides the complementary cutting blades 118, 120 withextremely tough, hard, wear resistant characteristics. This increasedhardness provides trimmer 110 with substantially increased longevity,while also providing the trimmer with corrosion resistance, as well asproviding a smooth and uniform appearance and color. Coating 132provides trimmer 110 with an aesthetically acceptable color orappearance and reduces friction between the cutting blades during use.

Coating 132 can be made of titanium nitride (TiN), chromium nitride(CrN), or titanium chromium nitride (TiCrN). More preferably, coating 32is a multiple component barrier of titanium chromium nitride.

Coating 132 having the desired hardness, smoothness, and diffusionbarrier properties preferably is formed of titanium chromium nitridehaving about 35 percent by weight of titanium nitride and about 65percent by weight of chromium nitride and with a hardness in a range afabout 5.7 to about 9.1 gigapascals. More preferably, coating 32 hasabout 50 percent by weight of titanium nitride and about 50 percent byweight of chromium nitride and a hardness in a range of about 7.2 toabout 7.6 gigapascals. Thus, coating 132 provides trimmer 110 with avisual indication that the coating had been applied, without affectingthe consumer's impression of the target use of the scissors (i.e.,general household use). Moreover, coating 132 provides trimmer 110 withdrastically improved hardness over uncoated trimmers.

An exemplary embodiment of a stationary cutting implement in the form ofa guillotine style paper trimmer 210 is illustrated in FIGS. 8 and 9.Trimmer 210 is as shown and described in U.S. Provisional ApplicationSer. No. 60/392,942 filed on Jul. 1, 2002, the contents of which areincorporated herein by reference.

Trimmer 210 has a base 212 and a pivoting cutting mechanism 214. Base212 has a fixed cutting blade 216. Pivoting cutting mechanism 214 has amovable cutting blade 220 pivotally secured to base 212 at a pivot point218. Each blade 216, 220 has a cutting edge 224. Accordingly, trimmer210 has a pair of complementary cutting blades 216, 220.

During use of trimmer 210, a piece of paper (not shown) is positioned onbase 212 so that the portion to be cut is disposed between the cuttingedges 224. Pivoting cutting mechanism 214 is moved about pivot point 218in the direction of arrow 226 such that the cutting edges 224 shear thepaper.

Cutting blades 216, 220 are preferably made of steel, more preferablystainless steel, such as 420 stainless steel. In addition, cuttingblades 216, 220 can be heat-treated to further increase the hardness ofthe complementary cutting blades.

Trimmer 210 has a coating 232 disposed on cutting blades 216, 220.Again, coating 232 has a thickness in a range between about 0.3 micronsand 0.5 microns, more preferably about 0.4 microns.

Coating 232, like coating 132, provides the complementary cutting bladeswith extremely tough, hard, wear resistant characteristics. Thisincreased hardness provides trimmer 210 with substantially increasedlongevity, while also providing the trimmer with corrosion resistance,as well as providing a smooth and uniform appearance and color. Coating232 provides trimmer 210 with an aesthetically acceptable color orappearance and reduces friction between the cutting blades during use.

Coating 232, like coating 132, can be made of titanium nitride (TiN),chromium nitride (CrN), or titanium chromium nitride (TiCrN). Morepreferably, coating 232 is a multiple component barrier of titaniumchromium nitride. Coating 232 is formed of titanium chromium nitridehaving about 35 percent by weight of titanium nitride and about 65percent by weight of chromium nitride and with a hardness in a range ofabout 5.7 to about 9.1 gigapascals. More preferably, coating 232 hasabout 50 percent by weight of titanium nitride and about 50 percent byweight of chromium nitride and a hardness in a range of about 7.2 toabout 7.6 gigapascals.

The coating described herein for stationary cutting implements providesa cost competitive manner to improve the hardness, longevity, stainresistance, and ease of use of the cutting implement. For example, ithas been found that the coating of the present invention, when appliedusing the aforementioned CAP process, increases the cost of the cuttingimplement by about seventeen cents, or less than 30% of the cost ofmanufacture the implement [sic].

It should also be noted that the terms “first”, “second”, and “third”and the like may be used herein to modify various elements. Thesemodifiers do not imply a spatial, sequential, or hierarchical order tothe modified elements unless specifically stated. While the inventionhas been described with reference to one or more exemplary embodiments,it will be understood by those skilled in the art that various changesmay be made and equivalents may be substituted for elements thereofwithout departing from the scope of the invention. In additions, manymodifications may be made to adapt a particular situation or material tothe teachings of the disclosure without departing from the essentialscope thereof. Therefore, it is intended that the invention not belimited to the particular embodiment(s) disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

1. A cutting implement comprising: a pair of complementary cuttingblades, each having a cutting edge; and a coating disposed on each ofthe complementary cutting blades, the coating having a multiplecomponent barrier of titanium chromium nitride.
 2. The cutting implementaccording to claim 1, wherein the coating has a thickness in a rangebetween 0.3 and 0.5 microns.
 3. The cutting implement according to claim1, wherein the cutting implement is selected from the group consistingof a pair of scissors, a rotary style paper trimmer, and a guillotinepaper trimmer.
 4. The cutting implement according to claim 1, whereinthe coating is deposited by a process selected from a group consistingof cathode arc plasma and reactive magnetron sputtering.
 5. The cuttingimplement according to claim 1, wherein the coating provides the cuttingblades with a satin silver appearance.
 6. The cutting implementaccording to claim 1, wherein the coating has a satin gold appearance.7. The cutting implement according to claim 1, wherein the cuttingimplement is a pair of scissors.
 8. The cutting implement according toclaim 3, wherein the blades are formed of a material selected from thegroup consisting of steel, stainless steel, 420 stainless steel,heat-treated steel, heat treated stainless steel, and heat treated 420stainless steel.
 9. A cutting implement comprising: a pair ofcomplementary cutting blades, each having a cutting edge; and a coatingdisposed on each of the complementary cutting blades, the coatingselected from the group consisting of titanium nitride, chromiumnitride, titanium chromium nitride.
 10. A cutting implement comprising:a pair of complementary cutting blades, each having a cutting edge; anda coating disposed on each of the complementary cutting blades, whereinthe coating includes titanium chromium nitride.
 11. The cuttingimplement according to claim 10, wherein the coating has a thickness ina range between 0.3 and 0.5 microns.
 12. The cutting implement accordingto claim 10, wherein the cutting implement is selected from the groupconsisting of a pair of scissors, a rotary style paper trimmer, and aguillotine paper trimmer.
 13. The cutting implement according to claim12, wherein the coating has a satin silver appearance.
 14. The cuttingimplement according to claim 12, wherein the coating has a satin goldappearance.
 15. A cutting implement comprising: a cutting blade having acutting edge; and a titanium chromium nitride coating disposed on eachof the complementary cutting blades, wherein the coating is applied tothe blades by a process selected from the group consisting of chemicalvapor deposition, physical vapor deposition, reactive magnetronsputtering, and cathode arc plasma.
 16. The cutting implement accordingto claim 15, wherein the coating has a satin silver appearance.
 17. Thecutting implement according to claim 15, wherein the cutting implementis selected from the group consisting of a pair of scissors, a rotarystyle paper trimmer, and a guillotine paper trimmer.
 18. The cuttingimplement according to claim 16, the coating further comprising titaniumnitride.
 19. A cutting implement comprising: a cutting blade, having acutting edge; and a coating having a satin silver appearance disposed onthe cutting blade, the coating comprising titanium chromium nitride,wherein the coating has a thickness in a range between about 0.3 toabout 0.5 microns.
 20. The cutting implement according to claim 19, thecoating further comprising titanium nitride and chromium nitride.